The Euclid project

Cristobal Padilla

Euclid is a mission for the European Space Agency (ESA) Cosmic Vision (CV) 2015-25 programme to explore how the Universe evolved over the past 10 billion years to address questions related to fundamental physics and cosmology on the nature and properties of dark energy, dark matter and gravity, as well as on the physics of the early universe and the initial conditions which seed the formation of cosmic structure.

Introduction

To accomplish its goals, Euclid will carry out a wide survey of 15,000 deg2 of the sky free of contamination by light from the Milky Way and the Solar System and a 40 deg2 deep survey to measure the high-redshift universe. The complete survey represents hundreds of thousands of images and several tens of Petabytes of data. Euclid will observe about 10 billion sources out of which more than one billion will be used for weak lensing. Several tens of million galaxy redshifts will be also measured and used for galaxy clustering. With these images Euclid will probe the expansion history of the Universe and the evolution of cosmic structures by measuring the modification of shapes of galaxies induced by gravitational lensing effects of dark matter and the 3-dimension distribution of structures from spectroscopic redshifts of galaxies and clusters of galaxies. Euclid data will provide improvement factors of ~30 in the measurement of the neutrino mass and up to ~400 in the uncertainty of the parameters of the cosmology state equation and will leave legacy catalogs in may areas of galaxy science with exquisite imaging quality and superb Near Infrared Spectroscopy.

Euclid Instruments

The Satellite will be equipped with a 1.2 m diameter Silicon Carbide (SIC) mirror telescope made by Airbus Defense and Space feeding 2 instruments, VIS and NISP, built by the Euclid Consortium. These instruments are a high quality panoramic visible imager (VIS), a near infrared 3-filter photometer (NISP-P) and a slitless spectrograph (NISP-S). The IFAE has been responsible for the design and manufacturing of the NISP Filter Wheel Assembly (NISP-FWA), a device that allows the NISP instrument to select the optical filter used for the images it takes.

Figure 2: The NISP instrument being assembled in the telescope structure

Figure 3: The NISP instrument being assembled in the telescope structure

IFAE contribution in 2021

During 2021, IFAE has continued its support to the integration of NISP inside the satellite. All tests have advanced well, and Euclid is currently scheduled for launch during the first half of 2023. The NISP-FWA is the first ever flight hardware for space built and qualified at IFAE. On another front, the group has continued activities inside the Euclid consortium to exploit the data and contribute to the scientific output of the mission. The activities have been focused in the analysis of the PAU data with Machine Learning techniques, where we have made studies on star-galaxy separation, background prediction and Photometric redshift measurements with deep learning techniques. In addition to the PAUS papers, we are in the process to publish a Euclid article on improving the broadband photometric redshifts using multi-task learning. Additionally, Cristobal Padilla is the chair of the Euclid Speaker’s Bureau and activities to build the software infrastructure to serve the consortium in this area have started within IFAE.

ASTEROID

ASTEROID is an H2020 project aiming at enabling Europe to acquire the technology and knowledge necessary to manufacture 2k^2 high performance Infrared Focal Plane Arrays, define the types of products to design and define the strategy to create an industrial manufacturing line of these detectors. IFAE is partnering with companies and institutions in France and Austria to develop a low noise and low dark current detector that will be directly useful for astronomy applications in both ground telescopes (ESO) or space telescopes (ESA).

IFAE’s responsibility is in the optical and electrical characterisation of the detector. During 2021, after the commissioning of all the equipment (cryo-vacuum, optical and ESO New Generation Controller readout systems) we have received the detectors from Lynred and have performed their characterization with up to 20 thermal cycles to measure its bond stability. The tests are still ongoing but preliminary results show that the detectors are stable with time and the stress of the thermal cycles performed. Therefore, development can continue to the next phase towards the industrialization of the product.

Thanks to this project IFAE has acquired the know-how in characterizing IR sensors for Astronomy and Space and established a possible link of future collaboration with other projects where IR detectors are needed. More information can be found in asteroidh2020.eu, maintained by IFAE as communication responsible of the project.

Figure 2: Lynred detector in its original packaging

Figure 3: Assembly of the Lynred detector (not visible) and its front-end electronics inside the IFAE cryostat with the needed insulation to achieve the temperature stability required for the tests.